Laser perimeter awareness system

ABSTRACT

A method of laser scanning a perimeter zone of a target site for the detection of potential threats comprises: scanning a pulsed laser beam across the perimeter zone; receiving echoes from the pulsed laser beam during the perimeter zone scan; deriving range data corresponding to the received echoes; determining position data of the received echoes in the perimeter zone; forming a scene image of a scan of the perimeter zone based on the range and position data of the received echoes thereof; repeating the steps of scanning, receiving, deriving, determining and forming for a plurality of perimeter zone scans to form scene images of each scan of the plurality; and comparing scene images of the plurality to detect a potential threat in the perimeter zone. In addition, a method of authenticating a potential threat detected in a perimeter zone of a target site comprises: detecting the potential threat and upon detection, interrogating the potential threat for a response by a wireless transmission; declaring the potential threat unauthorized if no response is transmitted wirelessly within a predetermined time interval from the interrogation; receiving the response, if transmitted, and determining if the response comprises a proper access code; and declaring the potential threat unauthorized if the received response is determined not to comprise the proper access code.

CROSS REFERENCE TO RELATED PATENT APPLICATIONS

U.S. patent application Ser. No. 10/109,372, filed Mar. 28, 2002, andentitled “Distributed Laser Obstacle Awareness System”;

U.S. patent application Ser. No. 10/251,422, filed Sep. 20, 2002, andentitled “Railway Obstacle Detection System and Method”;

U.S. patent application Ser. No. 10/347,908, filed Jan. 21, 2003, andentitled “System For Profiling Objects On Terrain Forward and Below AnAircraft Utilizing A Cross-Track Laser Altimeter”;

All of the above referenced patent applications are assigned to the sameassignee as the instant application.

This application is a divisional application of U.S. patent applicationSer. No. 10/440,918, filed May 19, 2003.

BACKGROUND OF THE INVENTION

The present invention is related to perimeter security and search andrescue systems, in general, and more particularly, to a system for andmethod of laser scanning a perimeter zone around a target site to renderan awareness of potential threats to such target site, and a system forand method of laser scanning a perimeter zone of water around a searchvehicle to detect an object floating in the water.

With the increase of worldwide asymmetric terrorist activities, close inand long range proximity identification of potential threats to a targetis of paramount interest. Today such threats may come in many forms suchas suicide bombers, car bombs, shoulder launched missiles, rocketpropelled grenades, and saboteurs among others. Terrorist targets suchas heavily populated civilian and governmental facilities, militarybases, aircraft, marine vessels and commercial businesses, for example,continue to expand worldwide. Likewise, these threats have alsoescalated in severity to now include real scenarios of chemical,biological, and nuclear attacks. As such, the role of intelligence,surveillance, reconnaissance, and countermeasure action has and willcontinue to be critical in preventing attacks on such targets.

In response to these emerging threats, it is of the ut-most importanceto proactively monitor the surrounding land and waterside perimeter ofthreat vulnerable targets. Specifically, potential target sites such asports and harbors, vast areas of land at airports and nuclear sites,military installations, high visibility sporting events, marine vessels,aircraft and others have come to the forefront requiring the detectionof object motion and presence. Early identification and warning ofobjects within a perimeter of a target is critical in assessingpotential threats and taking appropriate counter-terrorism/militarymeasures. As a result of our historically open society, terrorists havenumerous opportunities to strike our society at vulnerable targets whichheretofore may have only been passively monitored with a securitycamera, if at all.

Current perimeter security systems and processes have been demonstratedto be insufficient for these emerging threats. For example, videocameras, night vision systems, radar, and conventional security patrolshave proven ineffective at preventing recent terrorist attacks. Recentevents such as the bombing of the USS Cole, a French oil tanker inYemen, airport security breaches, car and suicide bombings, and thelaunching of rocket propelled grenades might have been avoided with anearly warning system capable of detecting and tracking motion of objectson the ground or water. In each case, assailants penetrated traditionalsecurity layers of manned surveillance, video camera, or no security atall to launch an attack. Early identification and geolocation ofpotential ground and marine threats may be critical in thwartingattempts and securing and sustaining economic, commercial and militaryoperations worldwide.

In addition, use of conventional radar systems for threat monitoring mayresult in confusion due to multi-path returns over water and will sufferfrom radar “clutter” at close in ranges (blind radar zones). These blindzones, depending upon the radar power, may be on the order of hundredsof meters to kilometers, for example. Additionally, changes in seastates can degrade the detection performance of the radar system evenfurther. Algorithms have been developed in an attempt to suppress thenoise generated due to multiple scattering paths from interaction withswells and short period surface wave action, but generally are targetedfor detection of large objects, such as ships, for example, over manykilometers. Further, radar systems also suffer from broad main beamlobes, on the order of 1-10 degrees. To generate this level ofdirectivity, side lobes can also be generated creating multi-pathpropagation, further reducing the fine detail detection of conventionalradar systems.

Also, as in the case of a search and rescue of a survivor at sea, like adowned pilot, for example, a person's body floating in water may bedetected by a conventional passive infrared system relying on thethermal difference between the body and the water. As the bodytemperature can be different than that of the water, the body of aterrorist may be detected by passive infrared sensors. However, the bodytemperature of a terrorist may be disguised. Once the body temperatureof the terrorist approaches that of the surrounding water, the abilityto detect the body with passive infrared sensors quickly diminishes,i.e. the thermal gradients necessary for an infrared body signature arelost. Thus, under these circumstances, conventional passive infraredimaging systems may miss detecting the terrorist's body in the water.

Likewise, in searching for persons in the water as in the case of asearch and rescue mission, while living, sufficient thermal gradientsmay exist to enable thermal detection of the person. However, oncedeceased, the body temperature approaches that of the water. In thiscase, use of thermal imaging for recovery is voided.

The present invention overcomes the aforementioned drawbacks of thecurrent perimeter security and search and rescue systems and provides alaser perimeter awareness system (LPAS) which utilizes a laser obstacleawareness system for monitoring a perimeter around a vulnerable targetfor rendering an awareness of potential threats to such target or formonitoring a perimeter of water around a search vehicle for detecting anobject floating in the water.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, a method oflaser scanning a perimeter zone of a target site for the detection ofpotential threats comprises the steps of: scanning a pulsed laser beamacross the perimeter zone; receiving echoes from the pulsed laser beamduring the perimeter zone scan; deriving range data corresponding to thereceived echoes; determining position data of the received echoes in theperimeter zone; forming a scene image of a scan of the perimeter zonebased on the range and position data of the received echoes thereof;repeating the steps of scanning, receiving, deriving, determining andforming for a plurality of perimeter zone scans to form scene images ofeach scan of the plurality; and comparing scene images of the pluralityto detect a potential threat in the perimeter zone.

In accordance with another aspect of the present invention, a system forlaser scanning a perimeter zone of a target site for the detection ofpotential threats comprises: a laser source for generating a pulsedlaser beam; a scanning unit for scanning the pulsed laser beam acrossthe perimeter zone and for receiving echoes from the pulsed laser beamduring the perimeter zone scan, the scanning unit operative to generateelectrical position signals corresponding to positions of the receivedechoes in the perimeter scan; a light detector for converting thereceived echoes into electrical echo signals representative thereof; asignal processor for receiving the electrical echo signals andcorresponding position signals and for forming scene image datacorresponding to a plurality of perimeter zone scans based on theelectrical echo signals and corresponding position signals; the signalprocessor operative to compare the scene image data of the plurality ofperimeter zone scans to detect a potential threat in the perimeter zone.

In accordance with yet another aspect of the present invention, a methodof authenticating a potential threat detected in a perimeter zone of atarget site comprises the steps of: detecting the potential threat inthe perimeter zone of the target site; upon detection, interrogating thepotential threat for a response by a wireless transmission; declaringthe potential threat unauthorized if no response is transmittedwirelessly within a predetermined time interval from the interrogation;receiving the response, if transmitted, and determining if the responsecomprises a proper access code; and declaring the potential threatunauthorized if the received response is determined not to comprise theproper access code.

In accordance with yet another aspect of the present invention, a systemfor authenticating a potential threat detected in a perimeter zone of atarget site comprises: a personal communicator for each person that hasaccess to the perimeter zone, each communicator operative to transmitwirelessly an authorized access code in response to a reception of awirelessly transmitted interrogation signal; a scanning laser objectawareness system (LOAS) for detecting the potential threat in theperimeter zone of the target site and for generating a threat detectionsignal indicative of the detection; a wireless transmitter/receiverunit; an authenticator unit coupled to the scanning LOAS and thewireless transmitter/receiver unit, and responsive to the threatdetection signal to control the wireless transmitter/receiver unit totransmit the interrogation signal to the potential threat; the wirelesstransmitter/receiver unit operative to receive the response, iftransmitted from a personal communicator within a predetermined area ofthe detected potential threat; the authenticator unit operative todeclare the potential threat unauthorized if no response is receivedwithin a predetermined time interval from the interrogation; theauthenticator unit further operative to declare the potential threatunauthorized if the received response is determined not to comprise anauthorized access code.

In accordance with yet another aspect of the present invention, a methodof laser scanning a perimeter zone of water from a search vehicle forthe detection of an object in the water comprises the steps of: scanninga pulsed laser beam across a surface of the perimeter zone of water;receiving echoes from the pulsed laser beam during the perimeter zonescan; deriving range data corresponding to the received echoes;determining position data of the received echoes in the perimeter zone;forming scene image data of a scan of the perimeter zone based on therange and position data of the received echoes thereof; and detectingthe object in the perimeter zone of water from the scene image data.

In accordance with yet another aspect of the present invention, a systemfor laser scanning a perimeter zone of water from a search vehicle forthe detection of an object in the water comprises: a laser source forgenerating a pulsed laser beam; a scanning unit for scanning the pulsedlaser beam across a surface of the perimeter zone of water and forreceiving echoes from the pulsed laser beam during the perimeter zonescan, the scanning unit operative to generate electrical positionsignals corresponding to positions of the received echoes in theperimeter scan; a light detector for converting the received echoes intoelectrical echo signals representative thereof; a signal processor forreceiving the electrical echo signals and corresponding position signalsand for forming scene image data corresponding to a perimeter zone scanbased on the electrical echo signals and corresponding position signals;and the signal processor operative to process the scene image data todetect the object in the perimeter zone of water.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an exemplary laser perimeter awareness systemsuitable for embodying the broad principles of the present invention.

FIG. 2 is a cross-section view of one of the laser perimeter zone scansof the embodiment of FIG. 1.

FIG. 3 is an illustration of a scan head suitable for use in theembodiment of FIGS. 1 and 2.

FIG. 4 is sketch exemplifying optical elements suitable for use in thescan head embodiment of FIG. 3.

FIG. 5 is a block diagram schematic of a laser perimeter awarenesssystem suitable for use in the embodiment of FIGS. 1 and 2.

FIGS. 6A and 6B depict a program flowchart suitable for use inprogramming a digital signal processor of the embodiment of FIG. 5.

FIG. 7 is a composite illustration of stored historical data of movingobjects over a plurality of scene images.

FIG. 8 is an exemplary queue table for prioritizing detected potentialthreats.

FIG. 9 is an illustration of an automated authentication system suitablefor embodying another aspect of the present invention.

FIG. 10 is a block diagram schematic of an exemplary authenticationsystem suitable for use in the embodiment of FIG. 9.

FIG. 11 is an illustration of a search and rescue application of thelaser perimeter awareness system from an aircraft search vehicle overwater in accordance with another aspect of the present invention.

FIG. 12 is an illustration of the laser perimeter awareness systemembodied on an aircraft search vehicle searching a 360° perimeter aroundthe search vehicle.

FIG. 13 is an illustration of a search and rescue application of thelaser perimeter awareness system on a marine search vessel in accordancewith another aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Developed initially for helicopters to avoid striking power lines andother ground obstacles, wide field scanning laser obstacle awarenesssystems such as the system disclosed in the U.S. Pat. No. 6,542,227,issued Apr. 1, 2003, for example, have been found applicable tomonitoring objects within a perimeter around a vulnerable target forthreat awareness and to search and rescue operations which will becomemore evident from the description found herein below. The aforementionedU.S. Pat. No. 6,542,227 which is assigned to the same assignee as theinstant application is hereby incorporated by reference herein forproviding greater detail of the structure and operation of an exemplaryscanning laser obstacle awareness system (LOAS). In the development andtesting of the LOAS over water several key phenomena were discovered. Asnoted in the aforementioned U.S. patent, the exemplary LOAS uses a 1550nm near-infrared wavelength laser with variable fields of view, adistributed fiber optic architecture, and an ability to detect very fineobjects at long ranges.

Moreover, when scanned over water at oblique incidence angles, specularreflection and absorption were noted from the water surface. Forexample, when the incident laser energy transmitted from the LOASstrikes the water surface, it is reflected in a direction other thanback to the laser receiver of the LOAS. However, floating objects in oron the water scatter this laser energy back into the direction of thelaser receiver. As such, only the floating objects will register a laserobject profile return when the LOAS is employed in this fashion. Thus,dominated by scattering, any object floating on the surface of the watercan result in a laser return. The level of the laser return is afunction of the object size, laser power, radiated beam divergence, andlaser receiver field of view. Testing has shown the ability to detectswimmers, waterfowl, and other small watercraft several hundred metersdown range of the LOAS.

With this discovery, the LOAS originally developed to detect power lineswhile in flight, may now be applied to scan the water surface to monitora perimeter about a target or zone thereof for potential threats or evenaid in the search and rescue of individuals lost at sea. Unlikeconventional passive infrared systems that rely on the thermaldifference between the body and water, using a LOAS in this fashion andexploiting the scattering and absorption characteristics thereof overwater can increase the detection performance, as it is independent ofthermal gradients which are needed for the detection of floating bodieswith passive infrared imaging systems as noted above. Using the laserscanning and return detection technologies to automate the searchpattern over water will generate a geo-located map of no laser echoes(water) and laser echoes (objects such as a terrorist, downed pilot ordebris).

Using a LOAS in this fashion exploits the very narrow emitted laser beamdiameter, on the order of 2 mrad of divergence, for example. Since theLOAS has been demonstrated to detect 5 mm wires at hundreds of meters(see U.S. Pat. No. 6,542,227), it clearly has the ability to detect finediameter objects at significant ranges. Exploiting this same performanceover ground or water will result in similar sensitivity and an abilityto detect small ground and/or waterborne objects.

Another noteworthy point is that a LOAS has none of the aforementionedlimitations of radar detection systems and can be used to detect thesame targets as the radar system with a very high degree of directivity,without side lobes or multi-path issues. Yet another very significantbenefit of employing a LOAS in perimeter security applications is theability to obtain very short range resolution, on the order of sixinches. This currently cannot be achieved using conventional radarsystems. Finally, it is possible to deploy an array of laser scanningdevices or heads in a LOAS for monitoring a perimeter completelysurrounding a target site with little or no inter-system cross-talkbetween scanning devices. More specifically, each laser scanner may bedesigned to emit and detect only a narrow band of optical frequencies.It is possible to place an array of scanners in close proximity byselecting a unique frequency, or channel, for each scanner. Cross-talkamong the scanners is reduced or eliminated through the use of standardoptical bandpass filters. The optical bandwidth of these filters can beone part in ten thousand, with an out-of-band rejection of 10⁵, forexample. Given this level of filter performance, it is possible to parsea large number of channels within the gain profile of many solid-statelasers (e.g. the C-band of Er:fiber lasers).

Yet another derivative of this technology is the ability to use the sameLOAS embodiment over water or land or combinations thereof. In eitherapplication, the laser echo returns can be compared to previouslymeasured returns to examine the scene for changes. With this level ofdetection performance, the device can be used to secure militaryinstallations over wide areas and present to security personnelinformation that relates to threats that have been identified bymovement, such as an intruder crossing a field.

When a LOAS is installed in a maritime environment, the same device canscan and monitor the perimeter of a ship, for example, for smallwatercraft or swimmers at ranges less than 3 km. This range is criticalas often a ship's radar performs better beyond 1 km due to near fieldground clutter returns. Once ground or waterborne objects have beendetected, it is possible to query other video and optical systems forconfirmation as will become better understood from the description foundherein below. Likewise, this object information can be fused with otherautomated fire control systems to suppress suspected threats.

FIG. 1 is a top view of a laser perimeter awareness system suitable forembodying the broad principles of the present invention. Referring toFIG. 1, a plurality of laser scanning devices 10, 12, 14, and 16 may bedisposed on a target 20 which may be a marine vessel, a building, anaircraft, a pier of a port and the like, for example. Each scanningdevice 10, 12, 14 and 16 covers azimuthally a correspondingly respectiveperimeter zone 22, 24, 26 and 28 with a scanning laser beam. Each zoneis bounded by lines of azimuth. For example, zone 22 is bounded byazimuth lines 30 and 32; zone 24 is bounded by azimuth lines 34 and 36;zone 26 is bounded by azimuth lines 38 and 40; and zone 28 is bounded byazimuth lines 42 and 44. Note that the zones may be overlapping inazimuth patterns. Each zone may also include an azimuth center line,like the dot-dashed line 46 shown for zone 26.

As shown in FIG. 2 which is a cross-sectional view of one of the laserperimeter scans of the embodiment of FIG. 1, each scanning device 10,12, 14 and 16 may oscillate its laser beam or path 50 back and forth inelevation covering an elevation angle θ which in turn scans the laserbeam across a ground or water perimeter line denoted as 48. Thus, as thelaser beam is scanned in azimuth and oscillated in elevation, it coversits respective perimeter zone with a sinusoidal pattern which may havean azimuth scan frequency of approximately two hertz (2 Hz), forexample. During each azimuth scan which may take on the order ofone-half second, laser energy is pulsed along the scanning beams orpaths at a predetermined rate which may be approximately 70,000 pulsesper second (pps), for example. Time of flight techniques on the laserechoes may be employed by the laser system to identify objects and thecorresponding locations thereof within the perimeter zone.

While the perimeter zones or scanned fields of view of the scanningdevices 10, 12, 14 and 16 of the embodiment of FIG. 1 are shown fixed,it is understood that they may be varied to respond to an emergingthreat. For example, it is well known that ports and piers in the US aresupported by a structural system of submerged pilings. Waterways betweenthese pilings permit access to swimmers and kayakers which presents apotential threat of sabotage. Thus, by varying the scan zone of ascanning device of the embodiment of FIG. 1 to a narrow corridor inazimuth, areas under a pier may be monitored in greater detail forintruders. Intruders in these areas may be detected using the laser backscatterings over water and a threat alert provided to render asituational awareness.

A laser beam scanning device suitable for use in the embodiments ofFIGS. 1 and 2 is illustrated in FIG. 3 and an exemplary embodiment ofthe optical components thereof is depicted in FIG. 4. Referring to FIG.3, a scan head 300 controls movement of the oscillating laser beam scanpattern at least along an azimuth axis 302 and an elevation axis 304.The extent of the laser beam oscillation in elevation angle θ is shownby the dot-dashed lines 306. A bottom 308 of the scan head 300 may bemounted to a surface of the target site, like the top of a building, forexample, such as shown in the sketch of FIG. 2. A window area 310 of thescan head 300 through which the beam scans are emitted would be pointedin the direction of the corresponding perimeter scan zone. A fiber opticcable 311 carrying the pulsed laser energy from a laser source, whichwill be described in greater detail herein below, may be passed into thescan head 300 through an opening 312 at the bottom 308 thereof orthrough an opening in a side area 320 described below.

Optical elements within the scan head 300, which will be described ingreater detail in connection with FIG. 4 below, cause the beams passedby the cable 311 to be oscillated in elevation through the scan angle θ.A conventional motor assembly (not shown) within the scan head 300controls movement of an upper portion 314 thereof an azimuth scan angleabout the axis 302 sufficient to cover the corresponding perimeter zone.This movement occurs along a seam 316 between the top and bottomportions, 314 and 308, respectively, and effectively moves theoscillating laser beams 306 along with the upper portion 314 whichprojects the beam scan pattern through a sinusoidal pattern much thesame as that described in connection with the example of FIG. 2.

Another portion 318 of the scan head 300 which includes the window area310 and falls within the portion 314 moves azimuthally with the portion314. Another conventional motor (not shown) disposed within the scanhead 300 controls movement of the portion 318 about the axis 304permitting control of the oscillating laser beams 306 in elevation, forexample, which may extend the perimeter zone outward from or inward tothe target site. In the present embodiment, the window area 310 of theportion 318 may be controlled to move upward and inside the portion 314to protect it from the environment when not in use. The corrugated skinor surface in the area 320 at the bottom portion 308 acts as a heat sinkto improve the transfer of heat away from the scan head 300 duringoperation thereof. Alternately, in the case where heat dissipation maynot be needed by the drive systems of the scan head 300, the side area320 may be smooth.

A sketch exemplifying the optical elements inside the scan head 300 isshown in FIG. 4. Referring to FIG. 4, the fiber optic cabling 311 may bealigned with the axis of the input aperture of a beam expander 322 toguide the laser beam therethrough. The expanded beam exiting theexpander 322 over optical path 324 may be reflected from an oscillatingmirror 325 over a scan of optical paths between path 326 and path 328about a central axis 330. The oscillated laser beams exit the scan head300 through the window 310. In the present embodiment, the oscillatingmirror 325 may be driven by a mechanically linked resonant scanner unit332 at an oscillation frequency of approximately one hundred hertz, forexample. Reference is made to the U.S. patent application No.10/056,199, entitled “Silicon Wafer Based Rotatable Mirror”, filed Jan.24, 2002, and assigned to the same assignee as the instant application,which application being incorporated by reference herein for providing asuitable resonant scanner and oscillating mirror assembly in greaterdetail. While the present embodiment uses a resonant scanner assemblyfor oscillating the laser beam, it is understood that other elements maybe used for oscillating the laser beam, like a transparent liquidcrystal scanner or microlens array scanner, for example, withoutdeviating from the broad principles of the present invention.

Return laser energy may follow the same optical scan paths as theiremitted beams for return to the optical fiber cable 311 as describedherein above. A bipolar laser beam return path may be embedded in thefiber optic cable 311. The window area 310 may comprise a clear, flat,zero power optical element made of a material like glass, for example,so as not to interfere substantially with the scan pattern of theexiting laser beams. In the present embodiment, the resonant scannerassembly 325,332 and window 310 are structurally coupled to movetogether along the azimuth path 334 and elevation path 336 to cause theoscillating laser beams 326-328 to move along therewith. In this manner,the oscillating laser beams are forced to move in azimuth with themovement of the scan head 300 to form a sinusoidal scan pattern shown at338. Also, in the present embodiment, the various scan motors forcontrolling the azimuth, elevation and oscillations of the laser beamswithin the scan head may include position sensing elements whichgenerate analog signaling of the specific position of the laser beam inthe controlled scan of the perimeter scan as is well known to all thoseskilled in the pertinent art, the significance of which being more fullyexplained hereinbelow.

While the scan head 300 of the present embodiment is described asutilizing a beam expander 332, it is understood that in someapplications, the beam expander 332 may not be used in which case, thepulsed laser beam exiting the fiber optic cable 311 may be guideddirectly to the oscillating mirror 325 over the path 324. The naturaldivergent expansion of the laser beam as it exits the fiber optic cable311 may provide a sufficient beam width. In some cases, a collimatinglens may be configured in the path 324 to stop the beam expansion andcollimate the beam prior to oscillation. Also, as noted above, thepresent invention may be embodied to include more than one scan head 300mounted at different locations on the target site as shown in FIG. 1.Depending on the application, some of the scan heads may utilize feweroptical elements and less scan angle than that described for theembodiment of FIGS. 1 and 2. It is also understood that the oscillationangle θ of the resonant scanner 332 may be controllably varied to becomenarrower or wider for different views.

A block diagram schematic of a laser perimeter awareness system (LPAS)suitable for use in the embodiment of FIG. 1 is shown in FIG. 5.Referring to FIG. 5, a common laser source 60 which may be aErbium:Glass fiber laser manufactured by IPG Photonics, for example, maygenerate laser energy on the order of 15 kilowatts peak power at a nearinfrared wavelength range of 1550 nanometers (nm), for example, and at apulse repetition rate of approximately 70,000 pps. The laser energypulses may be conducted from the common source 60 to the plurality ofscanning heads 10, 12, 14 and 16 over a distributed fiber optic patharchitecture 62 through conventional optical couplers, for example. Thescanning heads 10, 12, 14 and 16 scan the laser energy in laser beams orpaths over respective perimeter zones as described in connection withthe embodiment of FIGS. 1-4. Laser energy echoes received by each laserhead from its respective perimeter zone may be optically conducted overa separate or bipolar fiber optic path to a light detector. For example,laser echoes from head 10 may be conducted over a fiber optic path 64 toa light detector 66 and laser echoes from head 16 may be conducted overa fiber optic path 68 to a light detector 70. The other heads 12 and 14will have a similar arrangement. The light detectors convert thereceived light echoes into electrical analog signals representativethereof.

If inter-system cross-talk between the plurality of scanning devices isconsidered an issue, then the common laser source 60 may emit a narrowband of optical frequencies for each scanner and unique thereto. Thus,it is possible to place an array of scanners 10, 12, 14 and 16 in closeproximity by selecting a unique laser frequency band, or channel, foreach scanner. Cross-talk among the plurality of scanners may be reducedor eliminated through the use of standard optical bandpass filtersinternal to the optics of the scanner. That is, an optical bandpassfilter may be disposed in each scanner and designed to pass only thenarrow band of optical frequencies unique thereto for scanning andbackscatter reception. The optical bandwidth of these filters may be onepart in ten thousand, with an out-of-band rejection of 10⁵, for example.In an alternate embodiment, an individual laser source may be assignedto each scanner for emitting the narrow band of optical frequenciesunique thereto. Each individual laser source may be embodied eitherinternal or external to the scanner. Given the foregoing described levelof optical filter performance, it is possible to parse a large number ofchannels within the gain profile of many individual scanner solid-statelasers (e.g. the C-band of Er:fiber lasers).

In an alternate embodiment, an optical switch may be disposed in theoutput optical path of the common laser source 60. The optical switchmay be controlled to time multiplex the output laser beam of source 60to a plurality of fiber optic paths leading to the correspondingplurality of scan heads 10, 12, 14 and 16. Within each correspondingfiber optic path may be return optic fibers for receiving the returnlaser beam energy from the respective scan head and guiding it over adifferent optical path than the directed source laser beam. A suitablehigh-speed optical switch for this purpose may be a flip mirroredelement mounted with vertical hinges to be controlled in a horizontalrotation thereabout and mounted with horizontal hinges to be controlledin a vertical rotation thereabout. The optical switch may be fabricatedon a substrate using micro-electromechanical system (MEMS) techniqueswith miniature motors coupled to the hinged mountings for controllingthe movement of the mirrored element to direct the output laser beam toone of the scan heads 10, 12, 14 and 16 at any given time.

In this manner, the output laser beam from source 60 may be timemultiplexed among the aforementioned scan heads by controlling theoptical switch with a control signal which positions the motors of theswitch. Laser energy echoes may then be returned from the correspondingscan head over a separate or bipolar return path. It is understood thatthe flip mirror element is merely an exemplary embodiment of the opticalswitch and that other embodiments may be used just as well. For example,a rotating disc having a portion that is substantially clear to directpassage of the output laser beam along to one of the scan heads, and aportion that has a reflective coating to cause the beam to be reflectedto another scan head, such paths may be positioned by a motor controlledto direct the output laser beam to a designated scan head by passage orreflection thereof.

Also, in the embodiment of FIG. 5, each scanner 10, 12, 14 and 16generates azimuth (AZ) and elevation (EL) signals representative of theposition of the laser beam in its perimeter zone scan. For example,scanner 10 generates AZ and EL signals over signal lines 72 and 74,respectively, and scanner 16 generates AZ and EL signals over signallines 76 and 78, respectively. Each light detector conducts theelectrical echo signals thereof to digital inputs of a programmeddigital signal processor 80. For example, the echo signals fromdetectors 66 and 70 are provided to designated digital inputs of theprocessor 80 over signal lines 82 and 84, respectively. In addition, theanalog signals representative of AZ and EL from each of the scanners maybe digitized by an analog-to-digital (AID) converter and the digitizedAZ and EL signals provided to the processor 80. This may be performedautonomously by the A/D or under program control of the processor 80. Inthe present embodiment, each scanner may have its own individual A/D.For example, the AZ and EL signals from scanners 10 and 16 are digitizedby A/D converters 86 and 90 and the resulting digital AZ and EL wordsare provided to the processor 80 over data lines 88 and 92,respectively. The other scanners of the plurality will have a similararrangement. It is understood that a common A/D converter may be timemultiplexed for digitizing all of the AZ and EL signals from theplurality of scanners just as well. Moreover, if echo signal intensityis desired to a greater resolution than one-bit, as in the presentembodiment, for the processing of echo signals, then the outputs of thelight detectors may be digitized by an AID converter in a similar manneras described for the AZ and EL signals, for example. None of theaforementioned modifications will deviate from the broad principles ofthe present invention.

As will become more evident from the description below, each time theprocessor 80 receives an echo signal from a scanner, it stores thecorresponding AZ and EL positions thereof in the scan to form a sceneimage of the scan in a designated portion of a memory 94 coupled theretoover control, address and data lines 96, for example. The range of eachecho is determined by the processor 80 in the present embodiment usingwell-known time of flight techniques. Thus, the echo signals from thescanners are correlated and used to form scene images for each perimeterzone scan or portion thereof of each scanner. The echoes making up eachscene image may be considered picture elements or pixels for imageprocessing as will become more evident from the following description.

In the present embodiment, the processor 80 also controls thepositioning of a spotlight using a position control loop 98 to visuallytrack a high priority threat identified in one of the perimeter zones,and the positioning of a forward looking infrared (FLIR) camera or videocamera using another position control loop 100 for displaying a thermalor video scene surrounding the threat on a display to decision makingpersonnel. More specifically, a digital signal representative of adesired spotlight position may be output from the processor 80 oversignal lines 102 to a + input of a summer 104 which provides an errorsignal 106 to a spotlight position controller 108. In response to theerror signal 106, the controller 108 drives a spotlight assembly 110with signal 109 to a position to direct its light towards the identifiedthreat. An actual light position of the spotlight 110 is sensed andprovided as feedback to a − input of the summer 104 over signal line112. The controller 108 will drive the spotlight to its desired positiondesignated by signal 102 until the error signal 104 approachessubstantially zero and thereafter, vary the spotlight position inresponse to a varying desired position in order to visually track theidentified threat.

Likewise, a digital signal representative of a desired camera positionmay be output from the processor 80 over signal lines 114 to a + inputof a summer 116 which provides an error signal 118 to a camera positioncontroller 120. In response to the error signal 118, the controller 120drives a camera assembly 122, either FLIR or video or both, with signal124 to a position to view the identified threat within the field of viewthereof. An actual camera position of the assembly 122 is sensed andprovided as feedback to a − input of the summer 116 over signal line126. The controller 120 will drive the camera of assembly 122 to itsdesired position designated by signal 114 until the error signal 118approaches substantially zero and thereafter, vary the camera positionin response to a varying desired position in order to maintain theidentified threat in the field of view thereof. A video image of thecamera's scene is provided over signal line 130 to a display 132 via animage/text overlay circuit 134. In addition, data representative of theposition and the significance of an identified threat may be provided bythe processor 80 to a display controller 138 over digital signal lines136, for example.

The significance data of the threat may comprise parameters of shape,size and priority as will become more evident from the followingdescription. From the threat significance parameter data, the displaycontroller 138 may generate video signals representative of an image ofand corresponding text characterizing the threat together with aposition thereof in the video image. The generated threat video signalsmay be provided to the overlay circuit 134 over signal lines 140. In theoverlay circuit 140, the generated threat video signals may be displayedseparately in a map like image on the display monitor 132 orsuperimposed over the video signaling from the camera 122 for display onthe display monitor 132. Accordingly, responsible personnel may view thethreat(s) from the video images of the display monitor 132 and/or from avisual inspection of the spotlighted area and make a decision on whetheror not to take defensive counter-measures.

While the position control loops 98 and 100 have been described in theembodiment of FIG. 5 as being outside of the processor 80, it isunderstood that the functions described for the control loops 98 and 100may just as well be programmed into the processor 80 in an alternateembodiment. In such an alternate embodiment, the processor 80 wouldgenerate drive signals 109 and 124 directly, perhaps throughcorresponding digital-to-analog (D/A) converters, and receivecorresponding feedback signals 112 and 126 directly, perhaps throughanalog-to-digital (A/D) circuits. Also, if the position control loops 98and 100 are of the analog variety, a D/A converter may be included ineach summer 104 and 116 to convert the digital position signals toanalog, for example. The use of D/A and A/D circuits for these purposesis well known to those persons of ordinary skill in the pertinent art.

FIGS. 6A and 6B depict an exemplary program flowchart suitable for usein programming the processor 80 of the embodiment of FIG. 5 forperforming functions of the laser perimeter awareness system inaccordance with the broad principles of the present invention. Referringto FIGS. 6A and 6B, the program flow of blocks 152, 154 and 156 aresequentially executed in the background to follow in time the perimeterzone scans of the plurality of scanners, to gather the echo data fromthe received echo signals thereof which data comprising such parametersas amplitude, time of arrival (TOA), elevation (EL) and azimuth (AZ),for example, and to form an image scene for each complete scan. Thescans of the plurality of scanners may be performed simultaneously,preferably, but not necessarily, synchronized to each other, orsequentially around the perimeter in either a clockwise orcounter-clockwise direction. In either case, once a complete scan imageis formed as determined by block 156, an image complete flag is set andthe gathered data representative of the scan image is correlated to itscorresponding perimeter zone and stored in a designated portion ofmemory 94, for example. Note that there will be as many scan imagescenes as there are scanners and corresponding perimeter zones. Once thescene image data is stored in memory, the program resets the imagecomplete flag in block 158 and continues executing blocks 152, 154 and156 in the background to form the next scene image.

As each image scene is completed, decisional block 160 determines if areference image scene has been stored for the corresponding perimeterzone. If not, the current image scene may be classified as the referencescene image for the corresponding zone in block 162; else, the currentimage scene is stored and compared with the pre-classified referenceimage scene of the same zone in block 164 to identify moving objects. Areference image scene may be a composite of more than one image scene.The comparison of image scenes may be performed through well-known pixelanalysis algorithms comparing the position of the pixels of an object inthe current scene to the position of the pixels of the same object inthe reference scene. Thus, a change in position of the same object fromone scene image to another is indicative of movement thereof. Indecisional block 166, it is determined if there are any moving objectsidentified in an image scene. If not, processing is diverted to block162 in which the current image scene data may be classified as orcombined with the old reference image to form a new reference image forthe corresponding zone. The program then waits until data is gatheredfor the next complete image scene as determined by block 156.

If block 166 determines there are moving objects in the zone from thecurrent image scene, a moving object from those identified is selectedand the range, bearing and elevation thereof is determined in block 168.Next in block 170, it is determined if the selected object has beenpreviously identified. If not, the object is classified or tagged inblock 172 and a track flag is set for the tagged object in block 174.Since the object was not previously identified, it has no priorhistorical data from which to asses the threat thereof which will comefrom subsequent image scenes from the corresponding zone. Consequently,the threat analysis processing may be by-passed and processing maycontinue at block 176 in which it is determined if there are any moremoving objects identified from the current image scene.

If the selected object was previously identified as determined by block170, then it is next determined in block 178 if the track flag was setfor that object. If not, then the track flag is set in block 174. If thetrack flag was set, then this is an indication that the program istracking the movement of the object and has historical data from whichto determine a threat priority which is performed in block 180. In thepresent embodiment, the threat priority may be calculated based on awell-known constant bearing, decreasing range (CBDR) algorithm. Theillustration of FIG. 7 is a composite of stored historical data of twotagged moving objects, represented by small circles, over a plurality ofscene images. The target site is denoted by an X in FIG. 7. Each objectO in FIG. 7 is referenced by two subscripted numbers XY, where the Xsubscript identifies the tagged object and the Y identifies the sceneimage from which the position thereof was determined. For example, O₁₁represents object 1 taken from scene image 1, O₁₂ represents object 1taken from scene image 2 and so on. Likewise, O₂₁ represents object 2taken from scene image 1 and so on.

Both objects 1 and 2 are positioned with respect to the target site inthe illustration based on their range and bearing from a centerline(C/L) of the scan zone (see FIG. 1) for each scene image. For example,object O₁₁ is positioned at a range R₁₁ and a bearing angle −θ₁, objectO₁₂ is positioned at a range R₁₂ at the same bearing angle −θ₁ and soon. Similarly, object O₂₁ is positioned at a range R₂₁ and a bearingangle O₂₁, object O₂₂ is positioned at a range R₂₂ and a bearing angleθ₂₂ and so on. The dashed lines connecting the commonly tagged objects 1and 2 represent a track of the corresponding moving object. Accordingly,since object 1 is being tracked on a substantially constant bearing witha decreasing range with respect to the target site among scene images,it will have a higher threat priority than object 2 which is beingtracked as substantially traversing or moving away from the target.

After the threat priority for the moving object is set in block 182, itis queued into a table stored in a designated portion of memory 94 byblock 184. An example of such a queue table is shown in FIG. 8. Notethat objects are listed in the table from the highest to the lowestthreat priority. For example, in the table of FIG. 8, object 1 has thehighest threat priority denoted as 7, object 3 has the next highestdenoted as 5 and so on down the list. In the present embodiment, athreat priority of 10 may be representative of the highest and 0 thelowest, for example. The queue table listing may be updated in real timeas the program is being executed. For example, if object 1 startsdeviating in bearing away from the target X in subsequent scene images,the threat priority thereof will decrease and, consequently, its rowlisting in the queue table will fall. Next, in block 186, data on themoving object of the queue table listing may be output from theprocessor 80 over data lines 136, for example, to the display controller138 to effect its display on the screen of the display monitor 132. Theobject may be displayed in the form of a symbol or icon withcorresponding text characterizing its threat priority level.

Thereafter, in block 188, the shape of the moving object is determinedusing pixel analysis on the pixels of the current scene image,preferably through contrasting edges and lines as is well-known in thepertinent art. Next, in block 190, the object shape is compared, usingwell-known pixel pattern recognition techniques, for example, withpre-stored shapes or signatures of known objects which may be consideredfriendly objects, such as certain types of marine vessels, birds, andthe like, for example. The comparison may result in a match number ormatch percentage which may be used as the criterion for determiningwhether or not the object is friendly in decisional block 192. Ifdetermined not friendly, then in decisional block 194, it is determinedif the threat priority level of the object is above a predetermined Xlevel, like 7, for example. If so, position signals are output oversignal lines 102 and 114 to position the spotlight 110 to illuminate thethreat and camera 122 to view the threat, respectively, for visualtracking as described herein above. These position signals will continueto control the spotlight and cameras to track the threat until thepriority threat level thereof falls below the predetermined X level. Inthis manner, the threat may be visually inspected and confirmed byresponsible personnel, who may be alerted to the threat via the display132, for example, for making decisions on possible defensivecounter-measures. The responsible personnel may also determine from avisual inspection that the threat is not offensive or even friendly andavoid false alerts. All in all the system provides a sound situationalawareness of the perimeter surrounding the target site.

Of course, if the object is determined to be friendly by block 192, thenblocks 194 and 196 may be by-passed. In any event, program executioncontinues at block 176 in which it is determined if there are any moremoving objects in the current scene image. If there is another movingobject in the current scene, program execution continues at block 168and the steps 168-196 are repeated for the next object and so on untilall of the moving objects of the current scene are processed. When thereare no more moving objects in the current scene image to be processed,then the program execution waits until the next scene image is completedas determined by block 156 and the processing is repeated for the nextscene image as described herein above.

Accordingly, the LPAS identifies, tracks and profiles objects enteringthe various controlled zones of the perimeter of the target from metersto hundreds of meters away. In accordance with another aspect of thepresent invention, an automated authentication system may be included inor with the LPAS to permit a potential threat, once detected by theLPAS, to authenticate itself using such signaling as a coded assessradio frequency (RF) or infrared (IR) signal, entry card, or two-waypager, for example. On board the target, which may be an aircraft, ship,vehicle, building or the like, for example, a known list ofauthenticated access codes may be pre-stored for use in approving entryof and communicating back to the identified object. Denied entry mayresult in the generation of an alarm with subsequent rules of threatclassification and engagement. This authentication system would beparticularly useful in securing high value assets such as Air Force One,carriers, and special military aircraft operating in high ground orwater threat environments. The system may be also applied to thecommercial aviation industry.

In the commercial aircraft industry, for example, an aircraft may beequipped with a plurality of laser scanning laser heads as described inconnection with the embodiment of FIG. 1, for example. Thus, fourcontrolled zones may be established around the aircraft to monitor andtrack baggage handlers, fuel providers, food deliverers, and others.Once these individuals enter the controlled zones, they would beidentified by the LPAS and required to communicate an access code to theautomated authentication system disposed on-board the aircraft. This maybe performed by the identified individual with an automated RF tag idfrom a personal transmitter. The automated authentication system on theaircraft may then enter into an encrypted exchange with the identifiedindividual. Access authentication could be achieved with personneltwo-way paging, for example, to reduce system cost. If the exchange wasunsuccessful or if suspicious behavior is detected by the aircraft'sLPAS, notification may be sent to airport security. The authenticationsystem may have the capacity to store each entry, time, position, andother pattern information. This data set may be then communicated to theairport security office prior to departure of the aircraft for securityapproval. The data set may be stored on the aircraft and at the airportterminal and could remain active for a predetermined time period, like48 hours, for example.

FIG. 9 is an illustration of an automated authentication system suitablefor embodying this aspect of the present invention. In the embodiment ofFIG. 9, the target 20 may be an aircraft, for example, showing one ofthe plurality of laser scanning heads of the LPAS. The scanning head 10,12, 14 or 16 scans its laser beam 50 over a zone of the perimeter of theaircraft as described herein above. Within the zone, it may detect anobject 200 which may be a an authorized service provider or an intruder.The LPAS passes the position data of the detected object to anauthentication system 202 for authentication of the object 200.

FIG. 10 is a block diagram schematic of an exemplary embodiment of anauthentication system suitable for use in the embodiment of FIG. 9.Referring to FIG. 10, an authenticator unit 204 is coupled to an LPAS206 over a communication link 208 which may be hard wires, opticalfibers, wireless RF, wireless infrared, and the like, for example. Theauthenticator unit 204 may be coupled to a memory 210 over data lines212, to an encrypter unit 214 over data lines 216, and to a positioncontrol unit 218 of an antenna 220 over data lines 222. The memory 210may be used to pre-store authentication codes of various serviceproviders. In turn, the encrypter unit 214 is coupled aver signal lines226 to a transmitter/receiver unit 224 for the antenna 220. An exemplaryoperation of the embodiment of FIGS. 9 and 10 is as follows.

As the LPAS identifies the object 200 in a perimeter zone, it may passdata on the object 200 to the authenticator unit 204 over thecommunication link 208, such data including the location of the object200. In response, the authenticator unit 204 may send position signalingover lines 222 to the position controller 218 to position the antenna220 in the direction of the object 200. Concurrently, the authenticatorunit 204 may send a coded interrogation signal over lines 216 to theencrypter unit 214 which encrypts the interrogation signal and passes itto the transmitter portion of unit 224 over signal lines 226 fortransmission through antenna 220 to the object 200. The wavy line 230represents the interrogation transmission from the antenna 220 of thesystem 202.

If the object 200 is an authorized service provider, it will receive andrespond to the interrogation transmission 230 with its personalcommunicator which may be a hand-held two-way pager with the capabilityof transmitting a unique encrypted authorization code, for example. Thewavy line 232 in FIG. 9 represents an encrypted authorization codetransmission from the personal communicator of the object 200. Theencrypted transmission 232 is received by the receiver portion of unit224 via antenna 220 and passed over lines 226 to the encrypter unit 214wherein it is decrypted and passed to the authenticator unit 204 overlines 216. When the authenticator unit 204 receives the authorizationcode, it may compare it to the pre-stored authorization codes of thememory 210 to establish whether or not it is a proper authorizationcode. If an authorization code is not received from the object within apreset period of time or if the authorization code is not proper, thenthe authenticator unit may alert airport security, preferably by anencrypted signal transmitted over the antenna 220.

Moreover, if the received authorization code is determined to be proper,then the authenticator unit 204 may be operative to establish whetherthe service provider associated with the authorization code should be atthe location at the given time. The authenticator unit 204 may requestsuch information of the airport security, for example, via encryptedsignals transmitted from antenna 220 which may include the uniqueauthorization code of the service provider in question, for example.This information may be conveyed from the airport security to theautomated system 202 via antenna 220 in response to its request andpassed to the authenticator unit 204 via the receiver portion of unit224 and the encrypter 214. The authenticator unit 204 may then comparethe information received from airport security with what it hasdetermined to authenticate access of the service provider to theaircraft. If the authenticator 204 detects a discrepancy in thewhereabouts of the service provider, it will alert airport security viaan encrypted transmission. In this manner, the perimeter about a targetmay be monitored for intrusion by unauthorized personnel.

In summary, the LPAS of the present invention has many possibleapplications. For water security, the LPAS uses scanning laser beams andpulsed time of flight methodology to cover a given perimeter surroundinga marine vessel. Each laser beam is scanned azimuthally in a sinusoidalpattern across the corresponding perimeter zone using a resonant scannerwhich oscillates in a back and forth fashion at approximately 2 Hz., forexample. Laser energy is primarily reflected from the water surface awayfrom the scanner and is partially absorbed by the water. Water surfacebreaching objects scatter laser energy into the direction of thereceiving optics of the scanner. As such, the water can become invisibleto the laser energy due to scattering thereby making floating objectshighly visible. This implicit clutter reduction scheme exploits thephysical phenomena of specular reflection of laser light on water. Byexploiting the reflection of the laser energy on the surface of water,floating objects can be easily detected by the various scanners of theLPAS.

Likewise, using the variable scan field of view of a scanner of theLPAS, it is possible to scan very narrow corridors to monitor thewaterway under a pier for intruders, for example. Accordingly, the LPAScan scan these narrow corridors to detect these threats and provide anawareness thereof. Another side benefit of the surface scatteringmechanism of the various laser scanners of the LPAS is the ability toaid in anti-submarine warfare by sensing and tracking wake of periscope.Cavitation from the periscope and water craft propellers often result insmall bubbles. The assembly of these bubbles, white foam, results inback scattering of laser light (echoes) towards the laser receiver.These echoes remains as long as the bubbles are present, often lastingfor several minutes. Similarly, this can also be visualized fromwatercraft to detect the prior track.

Another application may be in search and rescue where individuals lostat sea may be detected using the LPAS to scan the laser beam over thewater surface at oblique incidence angles with a very narrow emittedlaser beam diameter, on the order of 2 mrad of divergence, for example.When the incident laser energy transmitted from the LPAS strikes thewater surface, it is reflected in a direction other than back to thelaser receiver of the LPAS. However, floating objects in or on the waterscatter this laser energy back into the direction of the laser receiver.Thus, dominated by scattering, any object floating on the surface of thewater can result in a laser return. As such, only the floating objectswill register a laser object profile return in an image scene which maybe conveniently detected when the LPAS is employed in this fashion. Thelevel of the laser return is a function of the object size, laser power,radiated beam divergence, and laser receiver field of view.

Accordingly, the LPAS may be applied to scan the water surface tomonitor a perimeter about a search vehicle or zone thereof for aiding inthe search and rescue of individuals lost at sea. Unlike conventionalpassive infrared systems that rely on the thermal difference between thebody and water, using a LPAS in this fashion and exploiting thescattering and absorption characteristics thereof over water canincrease the detection performance, as it is independent of thermalgradients which are needed for the detection of floating bodies withpassive infrared imaging systems as noted above. Using the laserscanning and return detection embodiments described herein above, thesearch may be automated by using the search pattern over water togenerate a geo-located map or image scene of no laser echoes (water) andlaser echoes to detect floating objects, such as a lost individual,downed pilot or debris, for example.

FIG. 11 is an illustration of an aircraft search vehicle 350, like ahelicopter, for example, having the LPAS disposed on-board with at leastone of the scanning heads 10 for monitoring a perimeter zone 352 of thewater for an object, like an individual 354 lost at sea, for example.The scanning head 10 may be similar to the scanning head 300 describedin connection with the FIGS. 3 and 4. However, some scan headapplications may not utilize the azimuth scan, but rather rely on themovement of the aircraft or other search vehicle for developing thesinusoidal scan pattern over a perimeter zone of water. When disposed onthe helicopter 350, the path of the emitted laser beam from the scanhead 10 may be tilted at an oblique incidence angle, like a 45 degreeangle, for example, to the water surface 356. Only floating objects,like the lost individual 354, will return the laser energy in thedirection of the scanning head 10 for post processing by the LPAS todevelop an image scene as described herein above. In some applications,the search vehicle 350 may include a plurality of scan heads 10, 12, 14and 16 to scan a 360° perimeter 358 of water under and surrounding thevehicle 350 searching for the lost individual such as shown in theillustration of FIG. 12.

This search and rescue application can occur from marine search vesselsas well. As shown in the illustration of FIG. 13, a marine vessel 360having the LPAS disposed on-board with at least one of the scanningheads 10 for monitoring a perimeter zone 362 in the water for anindividual 364 lost at sea. The scanning head 10 may be similar to thescanning head 300 described in connection with the FIGS. 3 and 4. Whendisposed on the marine vessel 360, the path of the emitted laser beamfrom scan head 10 may be tilted at an oblique incidence angle, like a 45degree angle, for example, to the water surface 356. Only floatingobjects, like the lost individual 364, will return the laser energy inthe direction of the scanning head 10 for post processing by the LPAS todevelop the image scene from which the object may be detected. In someapplications, the marine search vessel 360 may also include a pluralityof scan heads 10, 12, 14 and 16 to scan a perimeter of water surroundingthe vessel searching for the lost individual in a similar manner asdescribed in connection with the illustration of FIG. 12. In eitherembodiment, the control panel of the LPAS may include a search andrescue (SAR) button to automate the functionality of the laser scan.

A still further application is in maritime surveillance. It is knownthat in some cases, maritime vessels present the ship's name and homeport on the side of the vessel using reflective paint. In other cases,the company name is painted on the side. Typical commercial maritimevessels also use a black or IR absorbing paint on the hull to aid in thevisibility of the ship lettering over long distances. This combinationof highly reflective and absorbing paints, when used in conjunction witha scanning laser beam, allows one to read the lettering on the ship.Likewise, the side profile of the size and shape of the ship can be usedto further classify the vessel as noted herein above. This informationcan be used to feed other ground systems and as a method of confirmingmaritime traffic in an unattended manner.

A still further application is in the field of ground perimetersecurity. By laser scanning a perimeter surrounding a ground target withthe LPAS, a 3-dimensional image scene can be assembled in azimuth,elevation, and range from the received laser energy back scatterings asdescribed herein above. Scanning multiple times, on the order of every5-10 seconds, for example, a clutter map can be created whereby the datais accumulated and assembled from multiple passes. The accumulation ofdata may be then stored in a reference image, also know as a backgroundclutter map. Switching to real-time data, each image scene dataset ofazimuth, elevation, and range is compared to the reference clutter map.If the real-time data matches the clutter map to within a variabledistance of spatial resolution, no processed data is reported. Likewise,if no representative data point is present in the clutter map, adifference is noted and displayed on a geo-located map or aerialphotograph. If the target is moving and the data is accumulated anddisplayed over a period of time, a track can be displayed of a movingground object.

Using a LPAS in this fashion has a distinct advantage as it enables finedetail detection, high range resolution, and motion detection inconfined spaces where conventional radar is overwhelmed with groundclutter and can be hazardous to ground personnel. In addition, thisdetection technique has the ability to look beyond fence lines covertlyto see ground motion in non-secure areas.

A still further application of the LPAS is in short range airporttraffic control wherein the LPAS may be used in a fashion similar toground traffic control radar but over shorter distances, with finerdetection, and with a laser as the illumination source. Using thescanning laser beam, the area around the flight deck, for example, canbe scanned in real-time. Using the moving ground target capabilitymentioned above, it is possible to detect and track individuals, smallvehicles, and other objects such as wildlife that may be hazardous toaircraft operation or represent a potential terrorist attempt. The LPASmay be also installed on an aircraft using a distributed scanning head,fiber optic arrangement or installed on the ground to monitor around theaircraft. In each case the geo-located position is know and fromreturned laser energy, ground motion can be determined in azimuth,elevation, and range referenced to the area of interest. As such, securezones can be established and monitored. Whenever ground motion isdetected, an alarm is issued and acted upon by security personnel. Whenembodied in a security system, the times and locations of intrusions areestablished.

In addition, secure access can be automated with the automatedauthentication system using coded RF transmitters. When a moving objectpenetrates the secure zone, a transmitter on a personal communicator ofthe authorized user may issue an encoded key for access eitherautomatically or in response to a coded interrogation from the system.The encoded key or authorization code transmission is received andcompared to authorized access ID, time, spatial position, and motion.When access is authenticated, the alarm trigger may be de-activated.Conversely when no authentication can be made, an alarm can be issuedand airport security alerted. The alarm can be issued as a conventionalaudible alert or used by other visible cameras or sensors to furtherinterrogate the intrusion. By tracking the motion, logging theidentification, and comparing to the authorized access, a security logcan be recorded and analyzed. These actions would be undertaken in closeproximity to an aircraft or taxi way, within 1 km of range and a nominaloperating range of 100 m. Likewise, over longer ranges of airport land,intrusion is also of concern. By using the scanning laser methodology ofthe LPAS, it is possible to detect and track moving ground vehicles andsmaller objects not detected by conventional airport ground trafficradar.

While the present invention has been described above in connection witha number of embodiments, it is understood these embodiments werepresented merely by way of example and that in no way, shape, or form isany of the embodiments intended to limit the present invention. Rather,the present invention should be construed in breadth and broad scope inaccordance with the recitation of the claims appended hereto.

1-23. (canceled)
 24. Method of authenticating a potential threatdetected in a perimeter zone of a target site, said method comprisingthe steps of: detecting the potential threat in the perimeter zone ofthe target site; upon detection, interrogating said potential threat fora response by a wireless transmission; declaring the potential threatunauthorized if no response is transmitted wirelessly within apredetermined time interval from said interrogation; receiving saidresponse, if transmitted, and determining if the response comprises aproper access code; and declaring the potential threat unauthorized ifthe received response is determined not to comprise the proper accesscode.
 25. The method of claim 24 wherein the step of detecting includesdetecting the potential threat in the perimeter zone of the target siteby a scanning laser object awareness system.
 26. The method of claim 24wherein the step of interrogating includes encrypting a codedinterrogation signal; and transmitting the encrypted interrogationsignal to the potential threat.
 27. The method of claim 26 wherein thestep of receiving includes decrypting a transmitted coded responsesignal; and determining if the decrypted coded signal comprises theproper access code.
 28. The method of claim 24 wherein the interrogationis transmitted wirelessly using an RF carrier.
 29. The method of claim24 the interrogation is transmitted wirelessly using a coded light at apredetermined wavelength range.
 30. The method of claim 24 wherein thestep of determining if the response comprises a proper access codeincludes the steps of; extracting the access code from the receivedresponse; comparing the extracted access code with known proper accesscodes; and determining if the response comprises a proper access codebased on the result of said comparing step.
 31. The method of claim 24including the steps of: determining that the response comprises a properaccess code; determining a time of detection of the potential threat;and authenticating access to the potential threat based on said time ofdetection.
 32. The method of claim 31 wherein the step of authenticatingincludes: comparing the time of detection of the potential threat with aproper access time for the potential threat; and authenticating accessto the potential threat based on the result of said detection timecomparing step.
 33. The method of claim 32 including the step ofidentifying the proper access time based on the proper access code ofthe detected potential threat and a predetermined time schedule ofwhereabouts thereof.
 34. The method of claim 24 including the steps of:determining that the response comprises a proper access code;determining a position of the detected potential threat in the perimeterzone; and authenticating access of the potential threat based on saidposition.
 35. The method of claim 34 wherein the step of authenticatingincludes: comparing the detected position of the potential threat with aproper access position for the potential threat; and authenticatingaccess to the potential threat based on the result of said detectedposition comparing step.
 36. The method of claim 35 including the stepof identifying the proper access position based on the proper accesscode of the detected potential threat and a predetermined positionschedule of whereabouts thereof.
 37. A system for authenticating apotential threat detected in a perimeter zone of a target site, saidsystem comprising: a personal communicator for each person that hasaccess to the perimeter zone, each said communicator operative totransmit wirelessly an authorized access code in response to a receptionof a wirelessly transmitted interrogation signal; a scanning laserobject awareness system (LOAS) for detecting the potential threat in theperimeter zone of the target site and for generating a threat detectionsignal indicative of said detection; a wireless transmitter/receiverunit; an authenticator unit coupled to said scanning LOAS and saidwireless transmitter/receiver unit, and responsive to said threatdetection signal to control said wireless transmitter/receiver unit totransmit the interrogation signal to said potential threat; saidwireless transmitter/receiver unit operative to receive the response, iftransmitted from a personal communicator within a predetermined area ofthe detected potential threat; said authenticator unit operative todeclare the potential threat unauthorized if no response is receivedwithin a predetermined time interval from said interrogation; saidauthenticator unit further operative to declare the potential threatunauthorized if the received response is determined not to comprise anauthorized access code.
 38. The system of claim 37 including anencrypter unit disposed between the transmitter/receiver unit and theauthenticator for encrypting a coded interrogation signal prior totransmission and for decrypting a received coded response signal. 39.The system of claim 37 wherein the transmitter/receiver unit isoperative to transmit the interrogation signal wirelessly using an RFcarrier.
 40. The system of claim 37 wherein the transmitter/receiverunit is operative to transmit the interrogation signal wirelessly usinga coded light at a predetermined wavelength range.
 41. The system ofclaim 37 including a memory coupled to the authenticator unit forstoring the authorized access codes of the personal communicators; andwherein the authenticator unit is operative to extract the access codefrom the received response, to compare the extracted access code withthe stored authorized access codes; and to determine if the responsecomprises an authorized access code based on the result of saidcomparison.
 42. The system of claim 37 wherein the authenticator unit isoperative in response to the determination that the response comprisesan authorized access code, to determine a time of detection of thepotential threat; and to authenticate access to the potential threatbased on said time of detection.
 43. The system of claim 42 wherein theauthenticator unit is operative to compare the time of detection of thepotential threat with a proper access time for the person assigned thereceived authorized access code, and to authenticate access to thepotential threat based on the result of said detection time comparison.44. The system of claim 43 wherein the authenticator unit is operativeto identify the proper access time based on the authorized access codereceived from the detected potential threat and a predetermined timeschedule of whereabouts of the person assigned said authorized accesscode.
 45. The system of claim 43 wherein the authenticator is operativeto query a central security site for the predetermined time schedule ofwhereabouts of the person assigned the authorized access code of thereceived response signal.
 46. The system of claim 37 wherein theauthenticator unit is operative in response to the determination thatthe response comprises an authorized access code, to determine aposition of the detected potential threat; and to authenticate access tothe potential threat based on said position.
 47. The system of claim 46wherein the authenticator unit is operative to compare the position ofthe detected potential threat with an authorized access area for theperson assigned the received authorized access code, and to authenticateaccess to the potential threat based on the result of said detectiontime comparison.
 48. The system of claim 47 wherein the authenticatorunit is operative to identify the authorized access area based on theauthorized access code received from the detected potential threat and apredetermined schedule of whereabouts of the person assigned saidauthorized access code.
 49. The system of claim 48 wherein theauthenticator is operative to query a central security site for thepredetermined schedule of whereabouts of the person assigned theauthorized access code of the received response signal.
 50. The systemof claim 37 wherein the personal communicator comprises a two-way pager.51-65. (canceled)